The present invention relates to a free flowing detergent composition having a relatively high concentration of surfactant. More particularly, the present invention provides a free flowing detergent composition having a high concentration of a "low wash temperature" surfactant, which as used herein refers to a surfactant having relatively low melting and pour points.
There is a trend in the consumer products industry to use smaller packaging and container sizes. Reduced sizes conserve materials such as paper, cardboard, and plastic and are "environmentally friendly." This consumer preference trend for reduced package sizes, now occurring in the detergent industry, necessitates that more concentrated, higher bulk density detergent compositions be formulated. In order to formulate a concentrated detergent, it is necessary to utilize relatively high levels of surfactant to achieve comparable washing efficacy to a larger amount of a less concentrated, bulkier detergent composition. Moreover, it is desirable to employ relatively high levels of surfactants in detergent compositions as such increased concentrations generally improve the cleansing action of the detergent composition. However, such high surfactant loadings in granules or powdered detergents made according to prior art methods generally reduce the flowability of such detergents. Reduced flowability tends to decrease density by reducing optimal particle packing. Thus, a need exists for a detergent composition which has a relatively high concentration of surfactant and which has good flowability.
The consumer and the automatic washing appliance industry have moved toward employing colder wash temperatures as a means to obtain more energy efficient appliances and reduce operating costs. Such lower temperature washing necessitates the use of surfactants having lower melting points, pour points and viscosities than surfactants utilized previously. When incorporated in granular or powdered detergent compositions, such low wash temperature surfactants tend to detract from the flowability of the detergent composition more so than higher wash temperature, more viscous surfactants. Thus, there is a need for a detergent composition which utilizes the low wash temperature surfactants and which has good flowability. It would be especially desirable to provide a detergent composition which had a relatively high concentration of low wash temperature surfactants.
Prior artisans have attempted to formulate granular or powdered detergent compositions having relatively high surfactant concentrations as in U.S. Pat. No. 3,769,222 to Yurko et al. However, known prior art compositions with relatively high surfactant concentrations have limited flowability or achieve acceptable flowability by using more viscous, high wash temperature surfactants and/or undesirably high silica content (5-25% for Yurko et al.), which has low detergent functionality. Thus, there is a need for a method of formulating a detergent composition which has both a high level of low viscosity surfactant and a high flowability of the resulting powder.
Most granular detergents are presently produced by spray drying. This process involves slurrying of detergent components and spray atomization in a high temperature air stream. To minimize volatilization of nonionic surfactants in the spray tower, the detergent industry has focused its efforts on post-dosing. In post-dosing, one or more surfactants are added to the product after the spray drying operation. Usually, this method works well only for surfactants that are normally solid at the processing temperature. This practice limits the use of the low wash temperature surfactants (which are liquid at the processing temperature) whose inclusion is more desirable in some detergent compositions. Post-dosing of spray dried base material with low wash temperature surfactants, in amounts sufficient to provide satisfactory wash performance, generally results in poor flowing, aesthetically displeasing products. Moreover, the amount of low wash temperature surfactant that may be employed in the detergent formulation is severely limited. This limitation is undesirable, since, for heavy duty laundry detergents and particularly concentrated detergent compositions, it is advantageous to have large amounts or relatively high concentrations of surfactant present.